The present disclosure relates to processing adapted to determine a position of a focus lens and more specifically relates to the processing adapted to determine the position of the focus lens in an imaging device which follows a contrast autofocus system.
Currently available cameras adopt a technology which is also called an autofocus (AF) technology for automatically focusing on an object. As the autofocus technology, a phase difference AF system and the contrast AF system are mainly given.
In the phase difference AF system, light which enters the camera through a lens is split into two streaks of light and a position of a focus lens is determined from a space between two formed images. In the contrast AF system, the position of the focus lens is determined in such a manner that a contrast difference of an image that an imaging element generates is increased.
Incidentally, the imaging device which follows the contrast AF system has such an issue that in a case where a high-luminance object (for example, a fluorescent lamp, a streetlamp and so forth) is included in a subject, the focus lens is set to a position which is greatly displaced from a focus position.
As countermeasures to such an issue, for example, Japanese Unexamined Patent Application Publication No. Hei10-239581 discloses an imaging device that “a case where the maximum position of the focus evaluation value that two focus evaluation value peaks are present and the optical focus position do not mutually match is detected and the focus motor is driven in such a manner that the focus lens reaches the position where the focus evaluation value between the two peaks is minimized or the middle-distance of the autofocus lens that a failure is least likely to occur stochastically (see “ABSTRACT”).